Power transmission assembly with face mounted bi-directional shift clutches

ABSTRACT

A power transmission assembly includes an input member adapted to receive drive torque from a source of torque, an output member adapted to provide drive torque to an output device and a bi-directional roller clutch including a first ring fixed for rotation with one of the input and output members. A second ring is spaced apart from the other of the input and output members. Rollers are positioned in aligned cam tracks formed in facing surfaces of the first and second rings. Neither the first ring nor the second ring support the input member or the output member on the other. The second ring may circumferentially index relative to the first ring for causing the rollers to ride up the cam tracks and force the second ring to frictionally engage the other of the input and output members, thereby establishing a drive connection between the input and output members.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/084,285, filed on Jul. 29, 2008. The entire disclosure of the aboveapplication is incorporated herein by reference.

BACKGROUND

The present disclosure generally relates to power transmissionassemblies for use in automotive vehicles. More particularly, a powertransmission assembly with face mounted bi-directional shift clutches isdisclosed.

A number of vehicles have been assembled with manual transmission ortransaxle products. Typically, many development hours and dollars areexpended to precisely fit a transmission within a particular vehicle.Components connected to or positioned near the transmission haveparticular characteristics to function in concert with each other. If adifferent transmission is subsequently desirable, changes to multiplecomponents may be required depending upon the scope of the change of thetransmission.

Typically, many dollars and hours are associated with the design anddevelopment of the tooling required to produce the components of aparticular transmission design. Much of this tooling is dedicated toproducing only components associated with the specific transmission forwhich it was initially constructed. A design change may render thistooling less useful.

A number of dual clutch transmissions have been designed to automate theshifting process and provide a power shift between sequentially numbereddrive ratios. However, these transmissions may be substantially largerthan a corresponding manual transmission having the same number of driveratios. Other vehicle components may require modification to accommodatethe new larger transmission. Accordingly, it may be desirable to providean automated shift transmission sized to package within an existingmanual transmission envelope to further advance the field.

SUMMARY

The present disclosure describes a power transmission assembly includinga rotary input member adapted to receive drive torque from a source oftorque, a rotary output member adapted to provide drive torque to anoutput device and a bi-directional roller clutch. The bi-directionalroller clutch includes a first ring fixed for rotation with one of therotary input member and the rotary output member. A second ring isspaced apart from the other of the rotary input member and the rotaryoutput member. Rollers are positioned in aligned cam tracks formed infacing surfaces of the first and second rings. Neither the first ringnor the second ring support the rotary input member or the rotary outputmember relative to the other. The second ring is adapted tocircumferentially index relative to the first ring to cause the rollersto ride up the cam tracks and cause the second ring to frictionallyengage the other of the rotary input member and the rotary outputmember.

The present disclosure also provides a power transmission assemblyincluding a first clutch adapted to drivingly couple a power source to afirst input shaft and a second clutch adapted to drivingly couple thepower source to a second input shaft. First, third and fifth drive gearsare driven by the first input shaft. Second, fourth and sixth drivegears are driven by the second input shaft. First, second, third,fourth, fifth and sixth driven gears selectively drive a countershaft.The first through sixth drive gears are in meshed engagement with thecorresponding first through sixth driven gears. A plurality of firstthrough sixth bi-directional roller clutches are individually associatedwith respective first through sixth drive or driven gears and can beselectively actuated to establish at least six distinct gear driveratios between the first and second input shafts and the countershaft.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a schematic depicting a six-speed, dual clutch transmissionequipped with face mounted bi-directional shift clutches and constructedin accordance with the teachings of the present disclosure;

FIG. 2 is a schematic depicting an optional power take-off arrangementfor use with the transmission depicted in FIG. 1;

FIG. 3 is an exploded perspective view of a face mounted bi-directionalshift clutch;

FIG. 4 is a fragmentary cross-sectional view of the shift clutch shownin FIG. 3;

FIG. 5 is an exploded perspective view of another face mountedbi-directional shift clutch;

FIG. 6 is a fragmentary cross-sectional view of the clutch shown in FIG.5;

FIG. 7 is an exploded perspective view of another face mountedbi-directional shift clutch;

FIG. 8 is a fragmentary cross-sectional view of the clutch shown in FIG.7;

FIG. 9 is a schematic depicting a seven-speed, dual clutch transmissionequipped with face mounted bi-directional shift clutches of the presentinvention;

FIG. 10 is a schematic depicting an eight-speed, dual clutchtransmission equipped with face mounted bi-directional shift clutches ofthe present invention;

FIG. 11 is a schematic depicting an eight-speed, dual clutchtransmission having nested gears and bi-directional shift clutches;

FIG. 12 is an exploded perspective view of a bi-directional clutchinterconnecting rotatable shafts;

FIG. 13 is a fragmentary cross-sectional view of the clutch and shaftarrangement shown in FIG. 12;

FIG. 14 is an exploded perspective view of a bi-directional clutchdrivingly interconnecting telescopically arranged shafts; and

FIG. 15 is a fragmentary cross-sectional view of the shaft and clutcharrangement shown in FIG. 14.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

FIG. 1 is a schematic representing an automatic powershift transmission10 having a dual clutch 12 driven by a main shaft 14. During operationof dual clutch 12, torque may be transferred from main shaft 14 to oneor both of a first input shaft 20 and a second input shaft 22. Secondinput shaft 22 is shaped as a tube having at least a portion of firstinput shaft 20 extending therethrough. Various speed gearsets areselectively operable to transfer torque from one of first input shaft 20and second input shaft 22 to a countershaft 24. Power is transferredfrom countershaft 24 through a final drive 26 to a differential assembly28. Axle shafts 30 are each driven by differential assembly 28 and fixedfor rotation with a driven wheel (not shown).

Dual clutch 12 includes a first input clutch 32 and a second inputclutch 34. First input clutch 32 is selectively operable to transfertorque from main shaft 14 to first input shaft 20. Similarly, secondinput clutch 34 is selectively operable to transfer torque from mainshaft 14 to second input shaft 22. First input clutch 32 includes afirst drum 36 fixed for rotation with main shaft 14. A set of outerfirst clutch plates 38 are fixed for rotation with and axially moveablerelative to first drum 36. A set of inner first clutch plates 40 arefixed for rotation with a first hub 39. Inner first clutch plates 40 areaxially moveable relative to hub 39 and interleaved with outer firstclutch plates 38. Hub 39 is fixed for rotation with first input shaft20. A power-operated dual clutch actuator unit 41 is operable tocompress outer first clutch plates 38 with inner first clutch plates 40to transfer torque through first input clutch 32. Clutch actuator unit41 may be a purely electrical device, electro-mechanical orelectro-hydraulic without departing from the scope of the presentdisclosure

Second input clutch 34 includes a second drum 42 fixed for rotation withmain shaft 14. A set of outer second clutch plates 44 are fixed forrotation with and axially moveable relative to second drum 42. A set ofinner second clutch plates 46 are fixed for rotation with and axiallymoveable relative to a second hub 48. Hub 48 is fixed for rotation withsecond input shaft 22. Inner second clutch plates 46 are interleavedwith outer second clutch plates 44. Dual clutch actuator unit 41 isoperable to cause torque transfer through second input clutch 34 bycompressing outer second clutch plates 44 against inner second clutchplates 46.

A first speed gearset 50 can be selectively engaged to transfer torquefrom first input shaft 20 to countershaft 24. First speed gearset 50includes a first drive gear 52 fixed for rotation with first input shaft20. A first driven gear 54 is supported for rotation on countershaft 24.First drive gear 52 is in constant meshed engagement with first drivengear 54. A second speed gearset 56 includes a second drive gear 58 fixedfor rotation with second input shaft 22. A second driven gear 60 isrotatably supported on countershaft 24. Second drive gear 58 is inconstant meshed engagement with second driven gear 60. A third speedgearset 62 can be selectively engaged to transfer torque from firstinput shaft 20 to countershaft 24 and includes a third drive gear 64fixed for rotation with first input shaft 20. A third driven gear 66 isrotatably supported on countershaft 24. Third drive gear 64 is inconstant meshed engagement with third driven gear 66. A fourth speedgearset 68 can be selectively engaged to transfer torque from secondinput shaft 22 to countershaft 24 and includes a fourth drive gear 70fixed for rotation with second input shaft 22. A fourth driven gear 72is rotatably supported on countershaft 24. Fourth drive gear 70 is inconstant meshed engagement with fourth driven gear 72.

A fifth speed gearset 74 can be selectively engaged to transfer torquefrom first input shaft 20 to countershaft 24 and includes a fifth drivegear 76 rotatably supported on first input shaft 20 and a fifth drivengear 78 fixed for rotation with countershaft 24. Fifth drive gear 76 isin constant meshed engagement with fifth driven gear 78. A sixth speedgearset 80 can be selectively engaged to transfer torque from secondinput shaft 22 to countershaft 24 and includes a sixth drive gear 82rotatably supported on second input shaft 22 and a sixth driven gear 84rotatably supported on countershaft 24. Sixth drive gear 82 and sixthdriven gear 84 are in constant meshed engagement with one another. Areverse gearset 86 includes a reverse drive gear 88 fixed for rotationwith first input shaft 20. A reverse idler gear 90 is rotatablysupported on an idler shaft 92. Reverse drive gear 88 and reverse idlergear 90 are in constant meshed engagement with one another. A reversedriven gear 94 is rotatably supported on countershaft 24. Reverse drivengear 94 is in constant meshed engagement with reverse idler gear 90 suchthat countershaft 24 rotates in an opposite direction when in thereverse gear ratio as compared to the sixth speed ratios previouslydescribed. Transmission 10 also includes first, second, third, fourth,fifth, sixth and reverse shifting mechanisms. In particular, FIG. 1schematically depicts first through seventh face mounted bi-directionalshaft clutches 140, 142, 144, 146, 148, 150 and 152, respectively. Thebi-directional shift clutches will be described in detail hereinafter.

Final drive 26 includes an output drive gear 100 fixed for rotation withcountershaft 24 and an output driven gear 102 fixed for rotation with adrive member of differential assembly 28. Output drive gear 100 andoutput driven gear 102 are in constant meshed engagement with oneanother. As previously mentioned, differential assembly 28 transferspower to axle shafts 30. The gearing arrangement previously describedpermits selective establishment of six forward drive ratios and one reardrive ratio for a two-wheel drive powertrain. FIG. 1 depicts an optionalhypoid power take-off assembly 110 operable to transfer power from mainshaft 14 to another set of driven axles (not shown). Because hypoidpower take-off assembly 110 is optional, its components are shown inhidden line representation. Hypoid power take-off assembly 110 includesan output gear 112 fixed for rotation with a pinion shaft 114. Outputgear 112 is in constant meshed engagement with fifth driven gear 78. Apinion gear 116 is formed at one end of pinion shaft 114. A hypoid gear118 is in constant meshed engagement with pinion gear 116. Hypoid gear118 is fixed for rotation with an output shaft 120. It is contemplatedthat output shaft 120 is drivingly coupled to a secondary drive line toprovide torque to another set of driven wheels that are not associatedwith axle shafts 30.

FIG. 2 represents an alternate power take-off assembly 124 operable totransfer torque to another set of driven wheels other than thoseassociated with axle shafts 30. Hypoid power take-off assembly 110 maybe replaced with power take-off assembly 124 if a different gearpackaging arrangement is desired. Power take-off assembly 124 includesan output gear 126 fixed for rotation with a support shaft 128. Acrossed-axis, single enveloping worm gearset 130 transfers torque fromoutput gear 126 to an output shaft 132.

Operation of transmission 10 includes transferring power from main shaft14 selectively through various gearsets to provide first through sixthforward drive ratios as well as a reverse drive ratio. To provide powerat the first gear drive ratio, a first power-operated clutch actuator154 places first face mounted bi-directional shift clutch 140 in anactive mode where relative rotation between first driven gear 54 andcountershaft 24 causes first shift clutch 140 to lock and transfertorque. The remaining bi-directional shift clutches may remain or areplaced in an inactive or over-running mode such that torque is nottransferred from their respective gearsets to the shafts about whichthey rotate. Due to the dual input shaft arrangement previouslydescribed, second bi-directional shift clutch 142, fourth bi-directionalshift clutch 146 and sixth bi-directional shift clutch 150 may be intheir active mode positions with no detriment to transmission operation.This may occur because second input clutch 34 will be in the open ordisengaged position during transmission operation in the first forwardgear ratio. Dual clutch actuator unit 41 places first input clutch 32 inthe engaged or torque transferring position. As such, torque istransferred from main shaft 14 through first input clutch 32 to firstinput shaft 20. Power continues to flow through first drive gear 52,first driven gear 54, first bi-directional shift clutch 140,countershaft 24, output drive gear 100, output driven gear 102,differential assembly 28 and axle shafts 30. If transmission 10 isequipped with a power take-off assembly, torque transfers therethroughas well.

Prior to transferring torque through transmission 10 at the second geardrive ratio, a sequential up-shift from the first gear drive ratio tothe second gear drive ratio may be anticipated by pre-selecting theposition of certain shift mechanisms. To pre-select a sequentialup-shift from the first gear drive ratio to the second gear drive ratio,a second power-operated actuator 158 places second bi-directional shiftclutch 142 in the active mode to drivingly couple second driven gearwith countershaft 24.

Transmission 10 provides for power shifting between sequential driveratio positions. To execute a power shift, a time overlap exists betweendisengagement of first input clutch 32 and engagement of second inputclutch 34. Dual clutch actuator unit 41 causes simultaneous actuationand de-actuation of the clutches within dual clutch 12 to provide asmooth, uninterrupted flow of power to final drive 26. Once first inputclutch 32 is completely disengaged, first bi-directional shift clutch140 may be placed in the inactive mode. Because transmission 10 isequipped with a number of bi-directional shift clutches, pre-selectionof a next anticipated gear drive ratio is not required but may bedesired to minimize any power flow interruption.

A second gear to third gear shift is similarly accomplished. Inparticular, the third gear drive ratio may be pre-selected by energizinga third power-operated actuator 160 to place third bi-directional shiftclutch 144 in the active mode to drivingly couple third driven gear 66with countershaft 24. To shift from second gear to third gear, dualclutch actuator unit 41 disengages second input clutch 34 while firstinput clutch 32 is engaged. Once a third gear drive ratio isestablished, power flows from main shaft 14 through first input clutch32, first input shaft 20, third drive gear 64, third driven gear 66,third bi-directional shift clutch 144, countershaft 24 and final drive26 to differential assembly 28. Once the third gear drive ratio has beenestablished, second bi-directional shift clutch 142 may be placed in theinactive mode.

It should be appreciated that additional sequential up-shifts may becompleted in similar fashion to the shifts previously described. Fourth,fifth, sixth and seventh power-operated actuators 162, 164, 166 168cooperate with fourth, fifth, sixth and seventh bi-directional shiftclutches 146, 148, 150 and 152 to control transmission operation.Furthermore, transmission 10 is operable to shift from an odd numberedgear to an odd numbered gear or an even numbered gear to an evennumbered gear due to the presence of the first through sixthbi-directional shift clutches.

To obtain the reverse gear ratio, seventh bi-directional shift clutch152 is actuated by seventh power-operated actuator 168 to drivinglycouple reverse driven gear 94 with countershaft 24. To launch in thereverse direction, first input clutch 32 is engaged. Power istransferred from main shaft 14 through first input clutch 32, firstinput shaft 20, reverse drive gear 88, reverse idler gear 90, reversedriven gear 94, seventh bi-directional shift clutch 152, countershaft 24and final drive 26 to differential assembly 28.

FIGS. 3 and 4 depict first face mounted bi-directional shift clutch 140.The remaining bi-directional clutches are substantially similar to firstface mounted bi-directional shift clutch 140 and will not be describedin further detail. Bi-directional shift clutch 140 is a controllable,multi-mode, bi-directional overrunning roller clutch that is operable toselectively drivingly interconnect first driven gear 54 and countershaft24. It should be appreciated that first bi-directional shift clutch 140is used only as a torque transfer device and not for a gear mountingpurpose. In this manner, first driven gear 54 may be accuratelysupported for rotation on countershaft 24 by a bearing 180. Accuratealignment of first driven gear 54 provides a desired mesh between firstdriven gear 54 and first drive gear 52 to assure proper torque transferwith minimal noise, vibration or harshness being generated by the gearteeth engagement.

Bi-directional shift clutch 140 includes a hub 182 having a body portion184 positioned in splined engagement with countershaft 24. An extendedring portion or first ring 186 of hub 182 includes an inner cylindricalsurface 188 concentrically mounted on or in close proximity to acylindrical guide surface 190 partially defining an annular recess 192in first driven gear 54. Body portion 184 includes an outer surfacehaving a portion 194 that is shaped as a smooth cylinder.Axially-extending arcuate cam tracks 196 are formed on the outer surfaceof first ring 186 on hub 182 adjacent to cylindrical portion 194. Asecond ring or slider ring 200 is positioned within recess 192. Acorresponding plurality of axially-extending arcuate cam tracks 198 areformed on an inner surface of slider ring 200. A like plurality ofelongated cylindrical rollers 202 are retained within aligned sets ofcam tracks 196 and 198. Slider ring 200 is a split ring having an outercylindrical surface 204 selectively engageable upon expansion with aninner cylindrical surface 206 of recess 192. Slider ring 200 includes anactuation slot 208.

Bi-directional shift clutch 140 also includes a shifting sleeve 210 thatis rotatably supported on cylindrical portion 194 of hub 182. Shiftingsleeve 210 includes a first radially extending flange 212 and a secondradially extending flange 214 spaced apart from one another to define agroove 216. A lug 218 axially extends from flange 214 toward actuationslot 208. Shifting sleeve 210 is axially moveable upon actuation offirst power-operated actuator 154 between first and second positions. Atthe first axial position, lug 218 is positioned within actuation slot208. When shifting sleeve 210 is moved to the second position, lug 218is positioned outside of actuation slot 208. A shift fork (not shown) ispositioned within groove 216. First power-operated actuator 154 isoperable to translate the shift fork and move shifting sleeve 210between its first and second positions. Movement of shifting sleeve 210between its first and second positions places first bi-directional shiftclutch 140 in one of the active and inactive modes. In particular, whenshifting sleeve 210 is in the first position, lug 218 is positionedwithin actuation slot 208 to restrict relative rotation between sliderring 200 and hub 182. Thus, bi-directional shift clutch 140 is placed inits inactive mode where cam tracks 196, cam tracks 198 and cylindricalrollers 202 remain aligned with one another. As such, outer surface 204of slider ring 200 remains spaced apart from inner surface 206 of firstdriven gear 54 to continue to allow relative rotation betweencountershaft 24 and first driven gear 54 regardless of the speeddifferential between these components.

When first power-operated actuator 154 is commanded to translate theshift fork and move shifting sleeve 210 to its second position, shiftclutch 140 is placed in its active mode. In particular, lug 218 ispositioned outside of actuation slot 208. As such, relative rotationbetween countershaft 24 and first driven gear 54 causes hub 182 torotate relative to first driven gear 54 and slider ring 200. A limitedamount of relative rotation between slider ring 200 and hub 182 occurs.This limited relative rotational movement causes rollers 202 to ride upthe circumferentially indexed cam tracks 196 and 198 which, in turn,causes rollers 202 to exert a radially outwardly directed force onslider ring 200. As a result, the split slider ring 200 expands and itsouter surface 204 is driven into frictional engagement with innersurface 206 of first driven gear 54. Accordingly, shift clutch 140 islocked and first driven gear 54 is drivingly coupled to countershaft 24to transfer torque through transmission 10 at the first speed gearratio. It will be appreciated that bi-directional overrunning rollerclutch 140 can be used in virtually any power transmission assembly usedin vehicular drivetrain applications for the purpose of selectivelycoupling first and second rotary members.

FIGS. 5 and 6 depict another version of a bi-directional shift clutch atreference numeral 230. Bi-directional shift clutch 230 is substantiallysimilar to clutch 140. Accordingly, similar elements will retain theirpreviously introduced reference numerals. It should be appreciated thatclutch 230 may be used in place of any one of previously mentionedbi-directional shift clutches 140, 142, 144, 146, 148, 150 and 152.Bi-directional shift clutch 230 includes a hub 232 in splined drivingengagement with countershaft 24. Bearing 180 rotatably supports a drivengear 234 on countershaft 24. An axially extending ring portion 236 isintegrally formed with driven gear 234. A split slider ring 238 includesan outer cylindrical surface 240 selectively drivingly engageable withan inner cylindrical surface 242 of ring portion 236. A plurality of camtracks 252 are formed on an inner surface of slider ring 238. Acorresponding set of axially extending cam tracks 254 are formed on anouter surface of hub 232. A plurality of rollers 256 are in alignmentwith sets of cam tracks 254 and 252. A shifting sleeve 258 includes abody portion 260 slideably supported on an external surface 262 of ringportion 236. A groove 264 is formed in body portion 260 to receive theshift fork. A leg 266 radially inwardly extends from body 260substantially at a distance equal to a thickness of ring portion 236. Alug 268 axially extends from the distal end of leg 266 into an actuationslot 270 formed in slider ring 238. Shift clutch 230 functionssubstantially similarly to clutch 140 via axial translation of shiftingsleeve 258 to establish active and inactive modes.

FIGS. 7 and 8 depict another face mounted bi-directional shift clutchidentified at reference numeral 276. Clutch 276 is substantially similarto clutch 230. As such, like elements will retain their previouslyintroduced reference numerals. Clutch 276 differs from clutch 230 mainlyin the configuration of a shifting sleeve 278 being supported on anouter substantially cylindrically shaped surface 280 of hub 232 insteadof being supported on an outer surface of ring portion 236 on drivengear 234. An axially inwardly extending lug 282 extends from shiftingsleeve 278 and can be selectively positioned within actuation slot 270formed in split slider ring 238. Shifting sleeve 278 is axiallytranslatable to selectively move lug 282 between first and second axialpositions and place clutch 276 in one of its active and inactive modes.

FIG. 9 depicts a seven-speed automatic powershift transmission 300equipped with individual bi-directional shift clutches associated witheach speed gearset. Transmission 300 is substantially similar totransmission 10. As such, like elements will be identified with theirpreviously introduced reference numerals having an “a” suffix.Transmission 300 differs from transmission 10 by including a seventhspeed gearset 302 having a seventh drive gear 304 supported for rotationon first input shaft 20 a and a seventh driven gear 306 fixed forrotation with countershaft 24 a. Seventh drive gear 304 is in constantmeshed engagement with seventh driven gear 306. Additionally, an eighthbi-directional shift clutch 308 is selectively moveable by an eighthpower-operated actuator 310 to drivingly interconnect seventh drive gear304 with first input shaft 20 a. Further differences between thetransmissions include fifth drive gear 76 a being fixed for rotationwith first input shaft 20 a while fifth driven gear 78 a is rotatablysupported on countershaft 24 a. Fifth bi-directional shift clutch 148 ais also moved to coordinate with fifth driven gear 78 a.

The gears associated with obtaining a reverse gear ratio are alsodifferent within transmission 300 when compared to transmission 10. Inparticular, a first reverse idler gear 312 is fixed for rotation withreverse idler shaft 92 a and in constant meshed engagement with firstdrive gear 52 a. A second reverse idler gear 314 is supported forrotation on idler shaft 92 a. Second reverse idler gear 314 is inconstant meshed engagement with reverse driven gear 94 a. Reverse drivengear 94 a is fixed for rotation with countershaft 24 a. Seventhbi-directional shift clutch 152 a is operable to drivingly interconnectsecond reverse idler gear 314 with idler shaft 92 a to define thereverse gear ratio. Torque is transferred through transmission 300 toprovide a reverse gear ratio by actuating first input clutch 32 a totransfer torque from main shaft 14 a through first input clutch 32 a,first input shaft 20 a, first drive gear 52 a, first reverse idler gear312, seventh bi-directional shift clutch 152 a second reverse idler gear314, reverse driven gear 94 a, countershaft 24 a and final drive 26 a todifferential assembly 28 a. Transmission 300 may be equipped with anoptional power take-off assembly 320.

Power take-off assembly 320 includes an output gear 322 in constantmeshed engagement with reverse driven gear 94 b. Output gear 322 isfixed for rotation with a pinion shaft 324 having a pinion gear 326fixed at one end. A ring gear 328 is in constant meshed engagement withpinion gear 326 to provide torque to an output shaft 330. It should beappreciated that while power take-off assembly 320 is depicted as toinclude a bevel gear or hypoid gear assembly, other drive arrangementssuch as the cross axis single enveloping worm gearset 130 may beimplemented without departing from the scope of the present disclosure.

FIG. 10 depicts an eight-speed automatic powershift transmissionidentified at reference numeral 400. Transmission 400 is equipped withindividual bi-directional shift clutches associated with each speedgearset in a manner substantially similar to transmission 300.Transmission 400 differs from transmission 300 only in that an eighthspeed gearset 402 is included to provide an eighth forward speed gearratio. Eighth speed gearset 402 includes an eighth drive gear 404supported for rotation on second input shaft 22 b and an eighth drivengear 405 fixed for rotation with countershaft 24 b. A ninthbi-directional shift clutch 406 is moveable by a ninth power-operatedactuator 408 to selectively drivingly couple eighth drive gear 404 withsecond input shaft 22 b to provide the eighth speed gear ratio.Transmission 400 may also be configured as a two wheel drive or allwheel drive device in the manner previously described.

FIG. 11 depicts another eight-speed automatic powershift transmissionhaving individual bi-directional shift clutches associated with eachspeed gearset and identified at reference numeral 600. The axialpositioning of various speed gearsets has been varied when compared tothe transmissions previously discussed to reduce the overall length oftransmission 600. To further facilitate an axial length reduction,reduced diameter bi-directional shift clutches are used in conjunctionwith the larger of the drive or driven gear for a particular speedgearset such that at least a portion of the bi-directional shift clutchis nested within a pocket formed within the speed gear. The axial spaceoccupied by a nested speed gear and bi-directional shift clutcharrangement is less than the space occupied by the other speed gear andbi-directional clutch combination. The speed gearsets are substantiallysimilar to those previously described. As such, like elements willretain their previously introduced numerals including a “c” suffix.

The gearsets are arranged to not only minimize the overall axial lengthof transmission 600 but also the weight. As such, the length of secondinput shaft 22 c may be minimized by positioning each of the evennumbered gearsets closest to dual clutch 12 c. From right to left asviewed in FIG. 11, the gearsets are axially arranged in sequence assecond speed gearset 56 c, sixth speed gearset 80 c, fourth speedgearset 68 c, eighth speed gearset 402 c, seventh speed gearset 302,fifth speed gearset 74 c, third speed gearset 62 c, reverse speedgearset 86 c and first speed gearset 50 c. The relative axial positionof the various bi-directional shift clutches to other bi-directionalclutches as well as the axial position of each bi-directional shiftclutch relative to its respective speed gear may also allow furthernesting of components to reduce the axial length of transmission 600.Accordingly, the position of each bi-directional clutch will bedescribed.

First through ninth bi-directional shift clutch and actuator assemblies602, 604, 606, 608, 610, 612, 614, 616 and 618, are depicted in FIG. 11.The first through eighth bi-directional shift clutches are associatedwith the first through eighth speed gearsets, respectively. Ninthbi-directional clutch and actuator assembly 618 is associated withsecond reverse idler gear 314 c. To reduce the axial length required topackage second speed gearset 56 c, sixth speed gearset 80 c and theirrespective bi-directional shift clutches, second bi-directional shiftclutch and actuator assembly 604 is positioned in cooperation withcountershaft 24 c axially between second speed gearset 56 c and sixthspeed gearset 80 c. Sixth bi-directional clutch and actuator assembly612 is also axially positioned between second speed gearset 56 c andsixth speed gearset 80 c but is positioned in cooperation with secondinput shaft 22 c. The reduced axial length is achieved by positioningsecond bi-directional clutch and actuator assembly 604 within a pocket630 formed in second driven gear 60 c, positioning sixth bi-directionalclutch and actuator assembly 612 within a pocket 632 formed in sixthdrive gear 82 c and at least partially axially overlapping secondbi-directional clutch and actuator assembly 604 with sixthbi-directional clutch and actuator assembly 612.

Fourth speed gearset 68 c, eighth speed gearset 402 c, fourthbi-directional clutch and actuator assembly 608 and eighthbi-directional clutch and actuator assembly 616 are positioned in asimilar nested arrangement. For example, fourth bi-directional clutchand actuator assembly 608 is positioned within a recess 634 formed infourth driven gear 72 c. Eighth bi-directional clutch and actuatorassembly 616 is positioned within a recess 636 formed in eighth drivegear 404 c. Fourth bi-directional clutch and actuator assembly 608 andeighth bi-directional clutch and actuator assembly 616 at leastpartially axially overlap with one another as well.

To further reduce the axial length of transmission 600, fifth speedgearset 74 c, seventh speed gearset 302 c, fifth bi-directional clutchand actuator assembly 610 and seventh bi-directional clutch and actuatorassembly 614 are arranged as a nested package. It should also beappreciated that seventh speed gearset 302 c may be positioned in atleast a partially axially overlapping manner with eighth speed gearset402 c. In particular, seventh drive gear 304 c is positioned within apocket 640 formed in eighth drive gear 404 c. Similarly, eighth drivengear 405 c is positioned within a pocket 642 formed in seventh drivengear 306 c.

Fifth bi-directional clutch and actuator assembly 610 is positionedwithin a pocket 644 formed in fifth driven gear 78 c while seventhbi-directional clutch and actuator assembly 614 is positioned within apocket 646 formed in seventh drive gear 304 c. Fifth bi-directionalclutch and actuator assembly 610 at least partially axially overlapsseventh bi-directional clutch and actuator assembly 614.

Other condensed packaging arrangements include positioning thirdbi-directional clutch and actuator assembly 606 within a pocket 648formed in third driven gear 66 c. First bi-directional clutch andactuator assembly 602 is positioned within a recess 650 formed in firstdriven gear 54 c. Ninth bi-directional clutch and actuator assembly 618is positioned within a recess 652 formed in first reverse idler gear 312c.

Transmission 600 may be configured to provide torque to a two wheeldrive vehicle or may include a power take-off to provide drive torque toall four wheels of a vehicle. The power take-off may include a bevelgearset or a worm gear arrangement as shown in FIG. 2.

FIGS. 12 and 13 depict a power transmission arrangement 698 having aface mounted bi-directional shift clutch 700 operable to selectivelydrivingly interconnect a first shaft 702 with a second shaft 704. Thecomponents of clutch 700 are substantially similar to those previouslydescribed in relation to clutch 230. Differences between thearrangements include a hub 706 being fixed to or integrally formed withfirst shaft 702. Cam tracks 708 are formed on hub 706. A drum 710 isfixed to or integrally formed with second shaft 704. The remainingcomponents of clutch 700 are substantially similar to the components ofclutch 230 and are identified with like numerals.

FIGS. 14 and 15 depict another power transmission arrangement 750including bi-directional clutch 700 selectively drivinglyinterconnecting a first shaft 752 with second shaft 704. Shafts 752 and704 are positioned in a telescopic manner with second shaft 704rotatably supported on first shaft 752 by a bearing 756. Clutch 700depicted in FIGS. 12 through 15 functions substantially similarly toclutch 230 previously described.

Other features of the bi-directional shift clutches previously describedinclude that the hub, ring/drum and slider ring can be interchangeablyinternal or external in form. The lug that is set between the seam orsplit in the slider ring may be mounted on or in unison with the hub andcan be integral with the axially shifting sleeve.

Each face mounted bi-directional shift clutch can be modified for lengthand diameter based on packaging and torque requirements, since the gearradial location is supported by a bearing surface or assembly. Theroller diameter, length and count are determined by the torquerequirement, clutch housing diameter and length as well as the frictioncoefficient between the slider ring and the hub or drum. The ramp angleand form of the cam racks controls the radial force of the roller,engagement/disengagement rate, and slider ring to hub clearance gap fordrag torque or efficiency.

For automotive torque applications, most components may be produced withmetal material. The cam tracks can be integral, inserted or attached tothe drive or the driven members. Many cam track details can be processedwith powdered metal technology, stamping, rolling, forging, broaching,EDM, milling, grinding, shaping, or hobbing. The disengaging/engagingshifting sleeve may also be made from molded plastic with an integralmetal lug encased therein. This will eliminate the need for nylonpadding of metal shifting forks. The entire assembly can be producedwith plastics for low torque applications. The face mountedbi-directional shift clutch may be a direct replacement for thetraditional synchronizer/clutch assembly.

Furthermore, the foregoing discussion discloses and describes merelyexemplary embodiments of the present disclosure. One skilled in the artwill readily recognize from such discussion, and from the accompanyingdrawings and claims, that various changes, modifications and variationsmay be made therein without departing from the spirit and scope of thedisclosure as defined in the following claims.

1. A power transmission device comprising: a rotary input member adaptedto receive drive torque from a source of torque; a rotary output memberadapted to provide drive torque to an output device; and abi-directional roller clutch having a first ring fixed for rotation withone of the rotary input member and the rotary output member, a secondring spaced apart from the other of the rotary input member and therotary output member, and rollers positioned in aligned cam tracksformed in facing surfaces of the first and second rings, wherein neitherthe first nor second ring support one of the rotary members on the otherrotary member, the second ring adapted to circumferentially indexrelative to the first ring to cause the rollers to ride up the camtracks and cause the second ring to frictionally engage the other of therotary input member and the rotary output member.
 2. The powertransmission device of claim 1 wherein one of the rotary input memberand the rotary output member includes a recess in receipt of the firstring, the second ring and the rollers.
 3. The power transmission deviceof claim 2 further including an axially moveable shifting sleevesupported by one of the first and second rings.
 4. The powertransmission device of claim 3 wherein the shifting sleeve includes alug positionable within an actuation slot formed in the second ring toplace the bi-directional roller clutch in an over-running mode.
 5. Thepower transmission device of claim 1 wherein one of rotary input memberand the rotary output member includes a body having a toothed perimeterand a drum portion axially extending beyond the body.
 6. The powertransmission device of claim 5 further including an axially moveableshifting sleeve supported on an outer surface of the drum portion,wherein translation of the shifting sleeve places the bi-directionalroller clutch in one of an active mode and an inactive mode.
 7. Thepower transmission device of claim 6 wherein the shifting sleeveincludes a radially extending leg having a distal end fixed to anaxially extending lug, the lug being selectively positionable within anactuation slot formed in the second ring to place the bi-directionalroller clutch in the inactive mode.
 8. The power transmission device ofclaim 5 wherein the second ring is axially captured between one of therotary input member and the rotary output member and the shiftingsleeve.
 9. The power transmission device of claim 1 wherein the firstring includes a body portion fixed for rotation with the rotary outputmember and positioned adjacent the rotary input member.
 10. The powertransmission device of claim 5 wherein the first ring axially extendsbeyond the drum portion and supports an axially moveable shiftingsleeve.
 11. A transmission comprising: a first input shaft; a secondinput shaft; a first clutch adapted to drivingly couple a power sourceto the first input shaft; a second clutch adapted to drivingly couplethe power source to the second input shaft; a countershaft; first, thirdand fifth drive gears driven by the first input shaft; second, fourthand sixth drive gears driven by the second input shaft; first, second,third, fourth, fifth and sixth driven gears selectively driving thecountershaft, the first, second, third, fourth, fifth and sixth drivegears being in meshed engagement with the corresponding first, second,third, fourth, fifth and sixth driven gears; and first through sixthbi-directional roller clutches individually associated with respectivefirst through sixth drive or driven gears to provide first through sixthgear drive ratios to the countershaft.
 12. The transmission of claim 11wherein the first drive gear is rotatably supported by the first inputshaft, the first bi-directional roller clutch including a first ringfixed for rotation with the first input shaft, a second ring spacedapart from the first drive gear, and rollers positioned in aligned camtracks formed in facing surfaces of the first and second rings, thesecond ring adapted to circumferentially index relative to the firstring to cause the rollers to ride up the cam tracks and cause the secondring to frictionally engage the first drive gear and transfer torquebetween the first input shaft and the first drive gear.
 13. The powertransmission device of claim 12 further including an axially moveableshifting sleeve supported by one of the first and second rings.
 14. Thepower transmission device of claim 13 wherein the shifting sleeveincludes a lug positionable within an actuation slot formed in thesecond ring to place the first bi-directional roller clutch in anover-running mode.
 15. The power transmission device of claim 13 whereinthe first drive gear includes a body having a toothed perimeter and adrum portion axially extending beyond the body.
 16. The powertransmission device of claim 15 further including an axially moveableshifting sleeve supported on an outer surface of the drum portion,wherein translation of the shifting sleeve places the firstbi-directional roller clutch in one of an active mode and an inactivemode.
 17. The power transmission device of claim 16 wherein the shiftingsleeve includes a radially extending leg having a distal end fixed to anaxially extending lug, the lug being selectively positionable within anactuation slot formed in the second ring to place the firstbi-directional roller clutch in the inactive mode.
 18. The powertransmission device of claim 13 wherein the second ring is axiallycaptured between the first drive and the shifting sleeve.
 19. Thetransmission of claim 11 wherein each bi-directional roller clutch isselectively actuated by an associated first through sixth electricactuator.
 20. The power transmission device of claim 11 wherein thesecond ring is a split ring.